JPH0828489B2 - Array type infrared detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to an array type infrared detector, and more particularly to a structure of an array type infrared detector using an epitaxially grown semiconductor.

[Prior Art] It has been conventionally known that an infrared detector using a semiconductor, particularly _one using Hg _1-x Cd _x Te, has high sensitivity. Hg _1-x Cd _x Te in the infrared detectors using epitaxial (vapor phase, liquid phase etc.) grown Hg _1-x Cd _x
When using a Te single crystal, a CdTe substrate is widely used. The reason why CdTe is used as a substrate is Hg.
_There are good matching of lattice constants with _1-x Cd _x Te, and a semi-insulating substrate can be obtained.

An array type photovoltaic detector and a Si CCD (charge coupled device) are especially important as device configurations using Hg _0.8 Cd _0.2 Te crystals epitaxially grown on a CdTe substrate.
Alternatively, there is a hybrid configuration in which MOS switching elements are connected. Typical configurations include "SPIE" (SPIE), 443 (1983), 120, "IEEE Transactions on Electron Devices" (IEEETransactions o
n Electron Devices), ED-27 (1980), 154.

FIG. 2 shows a partial cross-sectional view of the infrared detector by these. In FIG. 2, 1 is a semi-insulating CdTe substrate, 2 is a p-type Hg _0.8 Cd _0.2 Te layer, 3 is a high concentration n formed in the p-type Hg _0.8 Cd _0.2 Te layer by ion implantation of boron or the like.
Mold layer (n ⁺ layer), 4 is a surface protective film, 5 is an indium pillar, 6
Is Si IC (CCD etc.), and 7 is infrared light.

In this example, Hg
It is a photodiode using an n ⁺ p junction of _0.8 Cd _0.2 Te, and can detect infrared light 7 with a wavelength of about 10 μm.
Since a large number of n ⁺ layers 3 are arranged, the photodiodes are arranged correspondingly. Furthermore, the signals from these individual photodiodes are injected into the SiIC 6 through the indium pillar 5 and read out to the outside.

In the case of this example, the part that detects infrared light in each photodiode is each n ⁺ p junction, but since the indium pillar 5 and SiIC6 are on the upper side in the figure, infrared light is detected from the upper side in the figure. It cannot enter the n ⁺ p junction. On the other hand, CdTe substrate 1
When it is semi-insulating, it is transparent to infrared light of about 10 μm, so that it is used with infrared light incident from the lower side in the figure.

[Problems to be Solved by the Invention] However, the above-mentioned array type infrared detector has the following drawbacks.

That is, in FIG. 2, the incident infrared light is p-type Hg.
_{The 0.8} Cd _0.2 Te layer 2 is absorbed on the side close to the CdTe substrate 1, and an electron-hole pair is generated at this portion. These electron-hole pairs reach the respective n ⁺ p junctions by diffusion and become the output of each photodiode. At this time, the electron-hole pairs diffuse not only in the vertical direction in the figure but also in the horizontal direction. Therefore, the electron and hole pairs generated by the absorption of infrared light at the portion where n ⁺ p junction does not exist directly above it are diffused to the n ⁺ p junction existing around it and the output of each photodiode is Become. In this case, the outputs of the photodiodes are in correlation with each other. Since each photodiode is each pixel of the array type infrared detector, there is a problem that crosstalk occurs between pixels and the resolution deteriorates.

The present invention has been made in view of the conventional circumstances as described above, and an object thereof is to provide an array type infrared detector having a good resolution and suppressing crosstalk between pixels.

[Means for Solving the Problems] In the present invention, a semiconductor layer having a narrow bandgap is formed on a semi-insulating semiconductor substrate, and regions having a conductivity type opposite to that of the semiconductor are arranged on the semiconductor layer. In a back-illuminated array type infrared detector in which infrared light is incident from the semi-insulating semiconductor substrate side, a region of the semiconductor substrate in which an opposite conductivity type region is not formed immediately above is heavily doped. It is an array type infrared detector characterized in that a formed layer is formed.

[Operation] Next, regarding the operation of the present invention, the semi-insulating semiconductor substrate is
An example will be described in which Te is used and a heavily doped CdTe n ⁺ layer is formed in the substrate region.

As mentioned above, semi-insulating CdTe is transparent to infrared light. This is because the band gap energy of CdTe is about 1.6 eV and the energy of infrared light to be detected (wavelength 10
This is because it is sufficiently large for about 0.1 eV for μm). However, in the case of an n ⁺ layer in which CdTe is doped with indium or the like at a high concentration as a donor, the number of free electrons becomes very large, and thus infrared light is absorbed by these free electrons. Therefore, this CdTen ⁺ layer 7 can absorb infrared light having energy smaller than its band gap energy. Therefore, if the thickness of this n ⁺ layer and the donor density are made sufficiently large, this
Infrared light incident on the n ⁺ layer is absorbed here.

The above-mentioned n ⁺ is formed immediately below the portion where the n ⁺ p junction, which is the portion for detecting infrared light in each photodiode, is not formed. Therefore, infrared light is incident only on the semiconductor layer immediately below the n ⁺ p junction, and an array type infrared detector with good resolution can be obtained.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a partial sectional view of an embodiment of an array type infrared detector of the present invention. In the figure, 1 is a semi-insulating CdTe substrate, 2 is a p-type Hg _0.8 Cd _0.2 Te layer, 3 is a high-concentration n-type layer (n ⁺ layer) formed in the p-type Hg _0.8 Cd _0.2 Te layer, 4 Is a surface protective film, 5 is an indium pillar, 6 is an IC (CCD or the like) of Si, 7 is infrared light, and 8 is a high concentration n-type layer (n ⁺ layer) of CdTe formed by indium diffusion or the like.

In this embodiment, the n ⁺ layer 8 is partially formed on the CdTe substrate 1.
After forming the p-type Hg
_{A 0.8} Cd _0.2 Te layer 2 is formed. Furthermore, the Hg in _0.8 Cd _0.2 Te layer 2 on the portion not forming the n ⁺ layer 8 Hg _0.8 Cd _0.2 Te
N ⁺ layer 3 is formed.

In the array type infrared detector formed as described above, an electron and a hole pair are not generated by the incident infrared light immediately below the part where np (n ⁺ p junction) is not formed. Therefore, the crosstalk between the pixels is suppressed, and an array type infrared detector with good resolution was obtained.

In this embodiment, the n ⁺ layer has been described as an example of the high concentration layer in the semiconductor substrate region, but a similar array type infrared detector can be obtained even if it is a p ⁺ layer.

[Effects of the Invention] As described above, in the array type infrared detector of the present invention, crosstalk between pixels is suppressed, and good resolution can be obtained.

[Brief description of drawings]

FIG. 1 is a partial sectional view of an embodiment of an array type infrared detector of the present invention, and FIG. 2 is a partial sectional view of an example of a conventional array type infrared detector. 1 …… Semi-insulating CdTe substrate 2 …… P-type Hg _0.8 Cd _0.2 Te layer 3 …… Hg _0.8 Cd _0.2 Ten ⁺ layer 4 …… Surface protection film 5 …… Indium pillar 6 …… SiIC layer 7 …… Infrared Light 8 …… CdTen ⁺ layer

Claims (1)

[Claims] 1. A semiconductor layer having a narrow bandgap is formed on a semi-insulating semiconductor substrate, and regions of a conductivity type opposite to that of the semiconductor are arranged and formed on the semiconductor layer. The semi-insulating semiconductor substrate side In a back-illuminated array type infrared detector from which infrared light is incident from, a highly-doped layer is formed in a region of the semiconductor substrate in which the opposite conductivity type region is not formed immediately above. An array type infrared detector characterized in that